I tear a piece of bark from the trunk of this half-decayed tree, and have disclosed amidst the rank-smelling damp and rotten wood, a large _Julus_, a slow-moving creature, with some hundred-and-fifty little twinkling feet. As this specimen has attained its adult condition, it must be at least two years old; for it does not acquire its reproductive organs and perfect development till that age.[70]

This creature has pa.s.sed through a rather curious history of evolutions.

The egg from which it was produced was lodged in a chamber excavated by the parent, a few inches below the surface of the rotten mould. From this egg proceeded a little kidney-shaped body, without limbs or motion, completely enveloped in a swathe of delicate transparent membrane. About a fortnight it remained in this helpless state, during which its organs had been forming out of the const.i.tuent cells, by repeated subdivision, and definite arrangement. At length it burst its cerement, and a minute Julus appeared, not more than 1/200th of an inch in length, composed of a head with antennae, and a body of eight segments, of which the first three carried each a pair of legs.

All the mult.i.tudinous limbs which we see in this adult have been produced in successive moultings, and all the numerous segments have been produced by the subdivision of the last but one,--that is the joint preceding the a.n.a.l one,--six at a time.

By the time the little animal was ready for the second sloughing, that is, in about a week after the preceding, three more pairs of feet were seen, which had budded from the fourth, fifth, and sixth segments, but which were as yet closely packed down beneath the investing skin; the seventh segment also was obscurely marked into six divisions. The skin was now thrown off, and these changes were perfected; the little Julus now had six pairs of feet, and thirteen segments.

This process was repeated again and again; the new limbs always developing on the segments last produced, and six new segments being always formed out of the existing penultimate. And by this gradual succession of development, the animal has attained the number of limbs and segments which we now perceive. The antennae and the eyes have likewise pa.s.sed through successive stages.

We have a right to infer the lapse of a period sufficient to produce these changes, for we see their indubitable results; but our inference would only lead us astray, because we have not allowed for a disturbing influence,--that of the Law of Creation. This is the Julus's first hour of life.

See, on the trunk of that towering _Cedrela_, a round hole, out of which a large Beetle is in the act of emerging. It is a n.o.ble _Buprestis_, encased in glittering mail, of the most refulgent metallic splendour, crimson, gold, and green. Can we find any clue to his age? Yes: the white grab has rioted and fattened in its burrows in the timber of this tree for many years; ever gnawing away with its h.o.r.n.y auger-like jaws the solid wood in tortuous galleries, which constantly enlarged, as it progressively grew, while its wake, as it advanced, was partially filled by its ordure. The old tree is, no doubt, perforated, through and through, by its winding corridors, as large as your middle finger. As soon as the vermin had pa.s.sed this his nonage, which, as I say, may have occupied a dozen years at least,[71] he sank into his short pupa-sleep, and here we see him paying his first visit to the light of day.

True; this is his first experience of daylight, and indeed of anything; for all the pupa-sleep and the larva-labour were prochronic in this case. The Beetle is just created.

Hark to that hollow roar! There is no mistaking that majestic sound. It is the voice of the many-sounding sea. Yonder through the trees we catch a glimpse of its shining face, and here we are at the verge of the cliffs, against whose feet the waves are breaking in white foam. We will clamber down to the rocks.

In this weed-fringed tide-pool there is a fine specimen of the Sh.o.r.e-crab (_Carcinus moenas_). It is a male just arrived at the perfection of adult age; its carapace smooth and wholly dark-green in hue, its under parts rufous orange. Its claws. are large and sharp; and the prompt.i.tude with which it presents these formidable weapons, extended to the utmost, shows how conscious it is of its warlike powers.

To all appearance this Crab is several years old;[72] I mean in this his present perfect or imago form. When this form was first a.s.sumed, the diameter of the carapace was not more than an eighth of an inch; it is now two inches; a great many periodical sloughings of the crust must have occurred to accomplish this sixteen-fold increase.

But four distinct metamorphoses were pa.s.sed before the commencement of this form. There was the Grapsoid form with the outline of the carapace nearly parallel-sided, and the dentations on the sides. Before this there was the Megalopa form, with the carapace ovate, and the abdomen projecting behind. Before this there was the Zoea form, with the carapace rising into a tall erect spine, sessile eyes, no claws, and the abdomen a slender jointed cord ending in a triangular plate. And before this, there was the egg, which was laid by the mother Crab, and carried by her for a considerable time attached to the false feet of her abdomen.

All these evidences of age, clear and unanswerable though they are, are yet fallacious, because the Crab has been created but this morning.

On this sea-washed branch of a tree, which has been blown off by some tempest, and carried into the ocean, there is a single Barnacle (_Lepas_). It consists of a hand of many pairs of fringed fingers, protected by a sh.e.l.l of five pieces, and a long flexible cartilaginous stalk, by the lower extremity of which it adheres to the timber.

The sh.e.l.ly valves are all crossed by strongly marked lines running over their surfaces in a direction parallel with each other, and with the outer margins of each valve. These, like the corresponding foliations in the tube of the _Serpula_, indicate the successive stages of growth; the outlines of every valve having stood at each of these growth lines in succession. On each of the scutal valves in this individual I can count about 260 growth-lines: if we suppose one of these to be made in a week,[73] and the increase to proceed uniformly throughout the year, we must conclude the valve to have been just five years in making.

[Ill.u.s.tration: LEPAS.]

This animal, like others we have already examined, had, moreover, a history before the first vestige of a valve was formed. It had pa.s.sed through several metamorphoses; in its pupa stage it had the form of a _Cypris_, and in this condition it first became adherent to the timber: before this it was a larva, having a general resemblance to another Waterflea, the _Cyclops_, especially in its younger stages: in this state it moulted several times. Nor was this the beginning of its life; for there was the still earlier condition common to all these cla.s.ses of animals, viz. that of the egg, which was laid and carried for some time by the parent Barnacle, and at length hatched while within the valves of her sh.e.l.l.

Thus, through a course of several years we are able to trace back the existence of this Cirriped, to its parent of a former generation. But our conclusions are altogether vitiated by the simple fact that this individual is the first of its species; it never had a parent; it never was an egg.

From the rocky pool before us I have picked up a rough pebble, the surface of which is incrusted with a delicate work of stony lace. This fabric, too fine to be resolved by the una.s.sisted eye, consists of the oval cells of a species of _Lepralia_. There are some hundreds of cells in this patch, which altogether does not cover a square inch of the pebble; and they are all made after one pattern, and set in a very regular manner, in quincunx. Each is a minute slipper-shaped box of stone, with the orifice set round with spines for the protection of the inmate, a transparent, elegant, and sensitive Polypide, which bears on its head a coronet of ciliated tentacles.

I am not going to describe the interesting structure and economy of this atom of life; but merely wish to direct your attention to one point,--the evidence which it affords of the lapse of past time.

Every one of these hundreds of stony cells, together with its living tenant, was normally produced by a process of gemmation; each having budded forth from the side of its predecessor as a k.n.o.b of clear gelatinous flesh, in the midst of which was developed, first the cell, and then the polypide,--the latter appearing in a rudimentary condition, and gradually acquiring its proper organs, before the orifice of the cell was opened.

I said every one of the cells was thus formed; but I ought to have excepted a single cell, which, though in nowise differing from the rest in form or structure, had a very different origin. This was the primal cell, and its beginning was as follows:

A minute atom of a scarlet hue, and of a semi-elliptical shape, was one day whirling round and round with rapid gyrations in the open sea. It was of soft consistence, covered with strongly vibrating cilia, and furnished with some stouter setae. After enjoying its motile instincts awhile, it settled down on this pebble, and became stationary. Presently it secreted and deposited calcareous matter around at, like a coating of the thinnest gla.s.s, the red parenchyma receding from the hyaline wall towards the centre.

Soon an orifice with thickened edges appeared on the upper side, and minute spines grew from the edges, which quickly lengthened. It was now a _Lepralia_ cell, and now the polypide was developed, and protruded its mouth from the orifice, surrounded by its elegant bell of ciliate tentacles. This solitary cell became the parent of hundreds more, by the gemmative process which I have already described.

But the red swimming atom;--whence came that? Well, it was shot out from the interior of a previous _Lepralia_, the result not of a gemmative but of a generative act. It originated in another patch similar to the one which incrusts this pebble, and that, in like manner, and by exactly similar stages, looked back to an anterior patch, and so on.

Plausible as this inference is, it is false; for the little aggregation of cells and polypides has been called into existence by the Divine _fiat_, this very instant.

We are still at the sea-sh.o.r.e. Within the long and narrow crevices into which these low-lying ledges of shale are split, innumerable tufts of sea-weed,--olive, purple, and green,--are perpetually waving in the wash of the sea. On one of these branching shrubs of _Phyllophora_, there is adhering, apparently cast there by accident, an irregular ma.s.s of pellucid jelly. It firmly cleaves to the alga, enclosing the bases of several branches within its firm but gelatinous substance.

This k.n.o.b of jelly is a compound animal of the genus _Botryllus_, and it has just been created as we see it. In order to understand its nature, look at it more closely.

Enclosed in the clear purplish-grey jelly, in the midst of scattered lighter specks, we see several star-like figures of bright hues, in which yellow and red are predominant; the symmetrical arrangement of which pleases the eye, and reminds us of some ornamental pattern designed by human art. Each star is composed of several (three, seven, ten or more) pear-shaped animals, with their smaller ends meeting in the centre around a common orifice, from which a current of water is discharged.

Now this a.s.semblage of animals bears evidence of progressive development. Some time ago a tiny egg was discharged from a parent _Botryllus_, which presently produced a little active tadpole-like larva, called a "spinule." This swam actively by means of its wriggling tail; but at length it settled head downward on this piece of sea-weed.

Immediately the head adhered, by an effused cement, to its support; the tail now gradually disappeared; and the round head, in the midst of a ma.s.s of jelly-like cement, began to display two orifices on its surface.

It soon a.s.sumed a pear-like shape, and thus the first _Botryllus_ was formed.

From the side of this "pear," another was developed by gemmation, and a third on the opposite side; the smaller ends of all were in contact, and the orifices of these extremities began to merge into one; while the large ends diverged. A fourth and a fifth "pear" were successively produced in the same mode, until a star or "system" was formed.

Meanwhile the surrounding ma.s.s of living jelly had been commensurately enlarging, and a new _Botryllus_, separate from the other star, had been produced in the jelly, which was the commencing point of a second system; and thus, by degrees, the compound ma.s.s of systems has grown to its present state of development.

[Ill.u.s.tration: BOTRYLLUS.

_a_, portion of one system and of a ma.s.s, on _Phyllophora rubens_; _b_, an egg _c_, spinule; _d_, the same, attached; _e_, the tail absorbed; _f_, the young _Botryllus_. All magnified.]

This process has been one of time: the adhesion of the "spinule" took place in about sixteen hours after its escape from the egg. The appearance of the two orifices was when the little animal was four days old; and by the end of a week a second "pear" had budded. The attainment of the present condition may have occupied about six months.

Nay; time has been no element in this development; it is prochronic development; it is the development of creation, not of nature.

Behold that ruffling of the smooth surface of the water; it is caused evidently by the forcible ejection of a current from some source a little way beneath the surface. Yes, it proceeds from the orifice in this ma.s.s of calcareous grit; where the protruding pipe of sh.e.l.l indicates the snug fortress of a _Clavagella_. I will carefully break away a little of the soft stone, and we shall see the curious structure more clearly. Ha! I have split off a piece which nicely exposes the whole burrow, without having materially injured the creature or his sh.e.l.l.

You see it is a bivalve Mollusk with one valve firmly imbedded and cemented into the stony wall of its chamber. But the hinder end of this valve is continued into a sh.e.l.ly tube, intended to protect the siphons, which is carried through the gallery forming the entrance into the chamber, and opens by a wide orifice in the free water outside. It is to this tube that I call your attention.

[Ill.u.s.tration: CLAVAGELLA.]

You observe that on its outer surface there are several foliated expansions of the sh.e.l.ly substance, surrounding it like so many frills at pretty regular intervals. Each of these foliations is a permanent record of a certain epoch. The terminal one is the margin of the tube-wall everted. The one below this was at some past period the eversion of the margin at what was at that time the extremity. The third frill had in like manner terminated the tube still earlier; and so with the fourth and fifth. It is impossible to look at these expansions, and not to believe that they have been formed in succession, in this way, by the periodic growth of the tube.

There was a time when, the first frill was not commenced; when the creature was a Mollusk with simple valves. But even this was not the beginning of its history. It was as a swimming Infusory with a broad ciliated disk, and a lashing _flagellum_, that the creature commenced its independent career; and it was doubtless in this condition[74] that it found its way into the burrow of some _Saxicava_. Here its tiny transparent valves were secreted; the left valve was soon cemented to the chamber; and then the creature began to secrete and form the tube around its siphons, which was progressively enlarged, and adorned at every stage of elongation by these witnessing frills--whose testimony is recorded in imperishable stone.

What can be more irresistible than such evidence as this? And yet we must take exception to it on the ground that this is the very hour of the animal's creation.

[Ill.u.s.tration: DIONE VENERIS.]

The elegant spinous sh.e.l.l-fish that we discern yonder, half-buried in the sandy floor of the sea--I mean that lilac-tinted p.r.i.c.kly Venus (_Dione Veneris_) needs no sh.e.l.ly protection for its siphons, which, as you may observe, are protruded to a great length. But a lesson not less instructive than that taught by the tube-frills of the _Clavagella_, is inculcated by the valves of the _Dione_. Near the hinder margin of each valve there is a ridge which runs from the beak to the front edge, a ridge which bears the series of long slender sh.e.l.ly spines, that imparts such a charm to this sh.e.l.l.

Each of these spines records an interval in the growth of the sh.e.l.l.

There are sixteen distinctly enumerable; each of which may possibly mark a year's growth. The increase of bivalves, however, is slow; and it may be that a longer interval than a year has intervened between spine and spine. For if we look more closely at this beautiful sh.e.l.l, we see that the whole exterior of both valves is marked with concentric foliated ridges, which are also indubitable lines of growth; and that these are twice or thrice as numerous as the spines, from one to five being intercalated between those which support the prolongations of the sh.e.l.ly substance.

Each of these concentric lines has a history. Every line, as well as every spine, has been produced by a protrusion and eversion of the glanduligerous edge of the mantle, which then secreted and poured out a copious deposit of calcareous matter along the margin of the previously existing valve. In this species each periodic deposit took the form of a ridge slightly elevated above the general surface; and, because the turned up margin of the mantle invested the edge of the valve already formed, therefore the new layer, with its elevated ridge, was concentric with the last edge, which was concentric with the previous one, and so on, the common centre of all being the beak (_umbo_) at the back of the valve.

The spines were formed in a manner essentially similar. At every second or third period of increase, the margin of the mantle, which is very versatile and protrusile, was thrust out, at the point which corresponds to the spines, into a long fleshy groove, by the reduplication of its edge. Within this groove the calcareous secretion was poured out; and after it had been allowed a few moments to harden or "_set_," the mantle-groove was cautiously withdrawn, and a new spine was exposed, as a produced end to the foliated ridge.

Yet, though this is the normal and natural mode of production, both of the concentric line and of the spines, it would be illusory to conclude that they have been so produced in the present example. The entire formation of the _Dione_ before us has been ab-normal and preter-natural: it has been _created_, not _born_: the whole development so legibly written on the sh.e.l.l has been prochronic.

There goes the Scorpion Stromb (_Pteroceras scorpio_), crawling over the rocks with protruded head and tentacles, and bearing his ma.s.sive house on his back. This sh.e.l.ly house of his will afford us a good example of structural development.